OFDEG. The linearity observed in the reduction of error for an artificially generated 200 bp DNA sequence, sampled at fixed intervals along its length. Each sampled error represents the Euclidean distance between the un-normalised OF profile of the entire sequence and that of a shorter sub-sequence. The reduction in error is linear for sub-samples that are less than approximately 80% of the sequence length, was similarly observed for sequences greater than 200 bp (data not shown). The gradient of this linear region is what we refer to as OFDEG.